python

Context processors add variables to every template context automatically. I create a function that takes request and returns a dict. This is perfect for site-wide settings like site name, current year, or user preferences. I add my processor to TEMPLA

I use clean_<fieldname>() to validate individual fields and clean() to validate field combinations. Raising ValidationError shows the message to the user near the appropriate field. For cross-field validation (like 'end date must be after start